Dielectric Constant Decreases Research Articles

Effect of tin doping on the structural, optical, and dielectric properties of unintentionally β-Ga2O3 single crystal

Abstract This paper studied the structural, optical, electrical, and dielectric properties of the undoped and 0.05 mol% Sn-doped β-Ga2O3 single crystals through comprehensive characterizations by X-ray diffraction (XRD), Raman scattering, Optical transmittance spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron (UPS) spectroscopy, and dielectric measurements. The optical bandgap decreases as Sn content increases. The results of XPS showed that Sn atoms were successfully added to the host β-Ga2O3 crystal. The position of the Fermi level of 0.05 mol% Sn-doped β-Ga2O3 is calculated to be 2.56 eV above the valence band and 1.85 eV beneath the conduction band. Also, the computed value of the work function of 0.05% mole Sn-doped β-Ga2O3 is 4.53 eV. AC conductivity increases, while dielectric loss and dielectric constant decrease with increasing frequency.

Pressure‐Induced Structural, Electronic, and Optical Properties of Lead‐Free NaGeX3 (X = F, Cl, Br, and I) Perovskites: First‐Principles Calculation

AbstractIn this study, the pressure‐induced structural, electronic, and optical properties of lead‐free inorganic Ge‐based perovskite materials NaGeX3 (X = F, Cl, Br, and I) through density functional theory (DFT) simulations conducted are explored with CASTEP. This research is driven by identifying perovskite materials with a tunable bandgap that are both efficient and non‐toxic for solar cell applications. The materials under consideration are found to be mechanically and thermodynamically stable, as per the Born stability criteria and formation energy calculations. This band structure analysis indicates these compounds exhibit semiconducting behavior with a tunable bandgap. Under ambient conditions, the Ge─X and Na─X bonds display covalent and ionic characteristics, respectively. Substituting halogens from F to I increases lattice parameters and a more covalent nature of the Ge─X bond. Concurrently, the bandgap narrows, transitioning from indirect (F) to direct (Cl, Br, and I). At the same time, the static dielectric constant rises, and both absorption and conductivity are significantly enhanced with a redshift in the optical spectrum. The application of tensile stress (positive pressure) increases both the lattice constant and bandgap, whereas the dielectric constant, absorption, conductivity, and reflectivity decrease. Conversely, compressive stress (negative pressure) induces the opposite effect. Pressure‐induced variations in the bandgap highlight the potential of NaGeX3 materials to significantly impact the next‐generation solar cells’ development, offering a pathway to more sustainable and efficient energy solutions.

Synergistic effect of WO3 on structural, physical, optical, and dielectric characteristics of multicomponent borate glasses for optoelectronic applications

This study demonstrates the promising potential of WO3-doped calcium lithium silicate borate glasses as a multifunctional material with adjustable characteristics for a range of current technological purposes. The melt quenching technique was used for the manufacture of calcium lithium silicate borate glass samples doped with WO3 with a chemical composition of (50-x)B2O3+10SiO2+15CaO+25Li2O + xWO3, where x = 0, 1, 2, 3, and 5 mol%. Raman spectroscopy and UV optical absorption methods were used to investigate the spectroscopic characteristics of glass samples. The dielectric characteristics of the produced glass samples were investigated by broadband dielectric spectroscopy (BDS) measurements. The extremely short-range ordering structural matrices revealed by X-ray diffraction have validated the amorphous nature. The Raman spectra of the calcium lithium silicate borate glass exhibit considerable differences from those of glasses containing WO3. The prepared glass samples exhibited an obvious relationship between the replacement of WO3 and their density and molar volume. As a result of a modification in the structure, the values of packing density (Vp) and oxygen packing density (OPD) decrease as the molar concentration of WO3 increases. The inclusion of WO3 increased the optical absorbance of the synthesized glasses, as demonstrated by UV–Vis optical absorption spectra. According to the dielectric characteristics, the dielectric loss and dielectric constant decrease with frequency, while the AC electrical conductivity exhibits a progressive increase.

The influence of hydrocarbons on the physical properties of sea bottom sediments of the Black Sea of different stages of diagenesis under conditions of high pressures and temperatures and the degree of saturation

The influence of hydrocarbons on the physical properties of sea bottom sediments of the Black Sea of different stages of diagenesis under conditions of high pressures and temperatures and the degree of saturation

Unravelling the Ageing Effects of PDMS‐Based Triboelectric Nanogenerators

AbstractAgeing of elastomeric materials in triboelectric nanogenerators (TENGs) often leads to compromised electrical performance and can greatly affect their real‐world application as next‐generation energy harvesters and self‐powered sensors. Herein, the ageing behavior of PDMS‐based TENGs is investigated by probing the dielectric and mechanical properties of the membrane materials. Over time, ageing of PDMS after 17 months is evinced by a decline by 71%, 68% and 52% in open‐circuit voltage, short‐circuit current and charge transfer, respectively, and an increase by 6.8 times in surface charge decay rate. The reduced electrical performance can be attributed to a decrease in work function, dielectric constant, surface adhesion and heterogeneity in stiffness, as well as an increase in loss tangent. The effect of chemical chain scission on the PDMS surface is confirmed through nearfield infrared nanospectroscopy. This study gives insights into the underlying mechanism behind the ageing of PDMS‐based TENGs, paving the way to future work for ameliorating these ageing‐related issues with the aim to ensure long‐term stability of practical triboelectric devices.

Experimental Study on the Dielectric Properties of Coal In Situ with Variable Temperatures.

The aim of this study was to explore the mapping relationship between the temperature and the dielectric parameters of coal and rock under variable temperatures as well as to determine the characteristics of a dielectric anomaly response. Experiments were performed using lignite, nonstick coal, gas coal, coking coal, and anthracite. The evolution of pyrolysis characteristics, microcrystal structure, and dielectric properties with changing temperature was investigated, and the changes in the dielectric parameters of coal and rock were comprehensively analyzed. As such, the cause of the dielectric anomaly with changing temperatures of coal and rock was revealed. The results show that the dielectric properties of coal at different pyrolysis temperatures are closely related to the degree of intermolecular thermal motion, the evolution of microcrystal structure, and the mechanism of polarization response. In the low-temperature stage, the thermal motion of coal molecules is weak and exhibits electronic polarization, and the dielectric parameters change slightly with temperature while being dependent on the moisture content. In the high-temperature pyrolysis stage, the intense molecular thermal motion leads to the breaking of chemical bonds and the release of volatiles; moreover, the distance between aromatic layers of coal decreases, the order of aromatic structure increases, the dipole turning polarization is the main polarization type, and the dielectric response is obvious. When the pyrolysis reaction is basically complete, the dielectric constants of the five coal samples reach the maximum. As the temperature increases continuously, the coal structure is destroyed by the weakening of the thermal motion of the coal molecules and the accumulation of thermal stress; meanwhile, the dielectric constant decreases gradually, while the dielectric loss and tangent of dielectric loss increase rapidly. At the same temperature, the dielectric constant decreases with an increase in test frequency. These results lay a foundation for the inversion of dielectric data in fire areas of coal mines.

Preparation and opto-electrical characterization of poly(ethylene oxide) based polymer blends for electrochemical applications

Solid polymer electrolyte blends with varied compositions of poly(ethylene oxide) (PEO)/carboxymethyl cellulose (Na-CMC) in 10/90, 50/50, and 90/10 compositions have been successfully prepared by means of the solution cast technique at room temperature. The modification of the structural, optical, and electrical properties of the prepared blend samples was studied by employing XRD, FTIR, UV-Vis, and electrical impedance spectroscopy methods. X-ray diffraction studies revealed that the crystalline nature gradually transforms into amorphous as the Na-CMC content increases in the sample. The variation of bands noticed in the Fourier transform infrared spectroscope characteristic spectrum of the blends reveals the formation of complexes between the individual polymers. The analysis of optical properties using a UV-Vis spectrometer in the wavelength range of 900–1100nm, shows a gradual decrease in the optical indirect energy band gap with an increase in Na-CMC content in the blend. The study of the electrical properties of the blend carried out in the frequency range 50 Hz–1MHz and temperature range 303K–338K, using an electrical impedance analyzer reveals that, the dielectric constant and loss decrease with the rise in frequency, exhibiting the usual behavior of the polymers. AC conductivity is found to increase with an increase in temperature. The highest value of ionic conductivity is found to be 6.06 × 10−3Scm−1 for the blend with a 10/90 composition.

Comparative Investigation of Pressure Effect on Structural Stability, Electronic and Optical Response of LaXO<sub>3</sub> (X = Al, In, Ga) for Optoelectronic Applications

A first principle study intense on the density functional theory with Heydscuseria-Ernzerhof screened hybrid functional hybrid function (HSEO6) is used to assess the structural, Electronic, elastic, mechanical and optical responses of LaXO<sub>3</sub> (X = Al, In, Ga) perovskite materials. The compressive investigation under the external static isotropic pressure (P= 0 to 80GaP), phase stability, band structure and their important impact on the optical response of LaAlO<sub>3</sub>, LaInO<sub>3</sub> and LaGaO<sub>3</sub>. Electronic band structure shows that LaXO<sub>3</sub> (X = Al, In Ga) semiconductor with indirect band gap and an optically inactive response up to 20GPa, while the band gap becomes direct at 80GaP. There are gamma points (G-X-Q) at 80GPa and the band gap changes from indirect to direct nature. Under main desperation physical parameters of perovskite materials are well explained the response of TDOS, PDOS and EPDOS contour plots have been well understood for the full description of the band gap. It is further observed that the external pressure enhanced upto 40GPa both materials are significantly more mechanically stable compared to pristine LaXO<sub>3</sub> (X = Al, In, Ga) at 0GPa. The optical properties of LaAlO<sub>3</sub>, LaGaO<sub>3 </sub>and LaInO<sub>3</sub>, dielectric coefficient <i>(ε<sub>1</sub>, iε<sub>2</sub>)</i> have been employed along with the optical responses like absorption, energy loss function, reflectivity and reflective index are obtained in the energy scale from 0 to 60 eV. It was observed that static dielectric constant decreases with the decrease in optical band gap. The optical tunings under the effect of pressure which are good candidates in practical optoelectronic applications are extensively used and interpreted by the calculation of the dielectric function.

Influence of Ni2+ ions on structural, spectral and dielectric properties of Sr–Co spinel ferrites synthesized by sol-gel auto-combustion route

Nickel substituted Sr–Co nano spinel ferrites with composition Sr0.5-xNixCo0.5Fe2O4 (0.0, 0.1, 0.2, and 0.3) were prepared with the help of a sol-gel auto combustion route. The prepared materials were sintered at 800 for four and a half hours. Analysis of XRD confirmed that the material is composed of a cubic spinel structure with a single phase, and its space group is Fd-3m. Rietveld refinement of X-ray diffraction data was done for all prepared compositions using FULLPROF software. As the composition under study contains more nickel than lattice constant, crystalline size, X-ray density, and bulk density decrease. The dielectric properties were observed about frequency. The dielectric properties revealed that dielectric loss, dielectric constant, and ac conductivity decrease with increasing the Ni2+ content. The activation energy (ΔE) was calculated from the slope of Arrhenius plots. The ΔE found in the range of 0.580–0.096 eV. The analysis of XPS was carried out to examine the elemental state of annealed samples. The prepared material is suitable for employment in applications involving high frequencies because the Ni-doped Sr–Co ferrites with the greatest Ni2+ concentration have the lowest dielectric loss, dielectric constant, and tangent loss value.

Effect of glass powder on mechanical properties and electromagnetic transmission properties of high alumina cement paste

The mechanical properties and electromagnetic transmission properties of high alumina cement (HAC) paste with different glass powder (GP) contents were investigated in this paper. The effects of hydration phase, unhydrated phase, GP phase and pore phase on the dielectric properties of HAC paste were quantitatively analyzed. The results show that the strength, fluidity and setting time of HAC paste decrease with the increase of GP replacement rate. The real part, imaginary part and loss angle tangent of dielectric constant decrease. The addition of GP leads to a reduction in reflectivity and absorptivity of electromagnetic waves in the paste, while increasing transmittivity.Furthermore, the real part of the dielectric constant of each phase in the HAC paste follows the order: hydration product phase > unhydrated phase > GP phase > pore phase. With an increase in GP content, the real part of the dielectric constant of the hydration product phase increases. Finally, based on the results of vector network analysis (VNA), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), the reasons for the changes of mechanical properties and electromagnetic properties of HAC paste under different GP replacement rates were analyzed from the aspects of phase composition, pore distribution and microstructure.

Change of Dielectric Constant of Highly Doped-Silica Glass Used in Optical Fibers with Frequency and Temperature Under the Effect of Polarization

In this study, the variation of the dielectric constant, i.e. relative permittivity of highly doped-silica glass used in optical fibers with frequency and temperature under the effect of polarization has been investigated. In this context, simulations of the relationship between the dielectric constant and both frequency and temperature have been carried out in the Matlab environment. According to simulation and theoretical analysis, it has been concluded that the dielectric constant of highly doped-silica glass tends to increase with the increase of ambient temperature. On the other hand, as the frequency of the source increases linearly, the dielectric constant decreases. Hence, the variations of highly doped-silica glass with temperature and frequency have been found to be 2.884 × 10-5 (°K)-1 and – 7.50 × 10-15 (Hz)-1, respectively. Moreover, in response to the change in frequency between 1011 Hz and 1012 Hz, the dielectric constant has taken values between 2.085 and 2.070. Additionally, for dielectric constant variations in 2.070 – 2.085 range, values of the relative change in polarization have been obtained in the range of 9.4695 × 10-12 F/m – 9.6023 × 10-12 F/m.

Energy-storage performance of NaNbO3-based ceramic capacitor derived from a high DOP glass network structure

0.75(0.4Na2O-0.1K2O-0.5Nb2O5)-0.25(0.87SiO2-0.13BaO) glass-ceramics were prepared by a traditional melting method to optimize the crystallization kinetics. We obtained a glass network with high degree of polymerization (DOP) by crystallization at different temperatures and achieved a high energy storage density. The increase of crystallization temperature has promoted the precipitation of ferroelectric phases Na0.9K0.1NbO3 and NaNbO3 with high dielectric constant (1200–2000), promoted the increases of grain size from 0.76 μm to 1.33 μm, and reduced the gap width from 3.71eV to 3.22eV. When the crystallization temperature increased to 1000°C–1100 °C, Ba2NaNb5O15 with low dielectric constant (∼460) increases, grain boundaries appear, and dielectric constant and BDS decrease. Among all the samples, the sample crystallized at 900 °C showed homogeneous and dense microstructure (grain size∼0.91 μm). The experimental data confirmed that the glass sample crystallized at 900 °C achieves low dielectric loss (<0.005) and high dielectric constant (∼122). The glass sample crystallized at 900 °C sample had a maximum energy storage density of 3.65 J/cm3, a power density of about 54 MW/cm3 and a super-fast discharge speed of 38 ns at 660 kV/cm.

Ni-modified BaTiO3 film prepared by sol-gel with high energy storage performance

The development of lead-free dielectric capacitors with high recoverable energy storage density and high energy storage efficiency is important for improving the overall performance of electronic and power systems. BaTiO3 (BTO) is one of the most common ferroelectric materials and has attracted much attention for energy storage applications in the past decades due to its excellent dielectric and ferroelectric properties. However, high remnant polarization and low electrical breakdown strength of BTO limit its development in energy storage applications. Many efforts (e.g., elements doping, interface/heterostructure, etc.) have been made to improve the energy storage density of BTO thin films. In this paper, Ba1-xNixTiO3 thin films (x = 0, 0.02, 0.04, 0.06, 0.08; abbreviated as BNxT) were synthesized via sol-gel and spin-coated method. The effect of Ni doping on the structural, dielectric, ferroelectric and energy storage properties of BTO thin films has been studied. The results confirmed that with the increase of Ni doping, a second phase arises and the dielectric constant decreases. While appropriate Ni doping led to the improvement of the breakdown strength, further increase of Ni deteriorated the energy storage because of the high oxygen vacancy. Finally, optimized energy storage performance was obtained for BN0.04T thin film: dielectric constant of 401, dielectric loss of 0.002, recoverable energy density of 20.2 J/cm3 and energy storage efficiency of 83.6% at 965 kV/cm. Meanwhile, the remnant and maximum polarization of the films were 0.06 μC/cm2 and 50 μC/cm2, respectively. BN0.04T thin film has an excellent application prospect and is expected to appear as a component in the future composite energy storage film system.

Temperature-dependent dielectric relaxation measurements of (acetamide + K/Na SCN) deep eutectic solvents: Decoding the impact of cation identity via computer simulations.

The impact of successive replacement of K+ by Na+ on the megahertz-gigahertz polarization response of 0.25[fKSCN + (1 - f)NaSCN] + 0.75CH3CONH2 deep eutectic solvents (DESs) was explored via temperature-dependent (303 ≤ T/K ≤ 343) dielectric relaxation (DR) measurements and computer simulations. Both the DR measurements (0.2 ≤ ν/GHz ≤ 50) and the simulations revealed multi-Debye relaxations accompanied by a decrease in the solution static dielectric constant (ɛs) upon the replacement of K+ by Na+. Accurate measurements of the DR response of DESs below 100MHz were limited by the well-known one-over-frequency divergence for conducting solutions. This problem was tackled in simulations by removing the zero frequency contributions arising from the ion current to the total simulated DR response. The temperature-dependent measurements revealed a much stronger viscosity decoupling of DR times for Na+-containing DES than for the corresponding K+ system. The differential scanning calorimetry measurements indicated a higher glass transition temperature for Na+-DES (∼220K) than K+-DES (∼200K), implying more fragility and cooperativity for the former (Na+-DES) than the latter. The computer simulations revealed a gradual decrease in the average number of H bonds (⟨nHB⟩) per acetamide molecule and increased frustrations in the average orientational order upon the replacement of K+ by Na+. Both the measured and simulated ɛs values were found to decrease linearly with ⟨nHB⟩. Decompositions of the simulated DR spectra revealed that the cation-dependent cross interaction (dipole-ion) term contributes negligibly to ɛs and appears in the terahertz regime. Finally, the simulated collective single-particle reorientational relaxations and the structural H-bond fluctuation dynamics revealed the microscopic origin of the cation identity dependence shown by the measured DR relaxation times.

Rietveld analysis and dielectric spectroscopy of high conductivity and low dielectric loss Co Zn La ferrite

ABSTRACT This study investigates structural and dielectric characteristics of Co0.65Zn0.35LaxFe2-xO4 (CZL), with (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1), synthesized using the flash auto-combustion approach. The Fourier transform infrared spectroscopy supports the X-ray results for forming single-phase spinel structure. The Debye Scherer’s formula was used to evaluate the average crystallite size that found within the range of 31.5–46 nm. With increasing La3+ concentration, the lattice parameter, cell volume and density decreased. The formation of nanoparticles was supported by transmission electron microscopy TEM examination, which was coinciding with nanoparticle size from (XRD) data. The sample x = 0.06 has the highest value of resistivity and the lowest dielectric loss. The high value of electrical resistivity in ferrite is suitable for the high frequency application where eddy current losses are appreciable. The dielectric constant decreases with increasing La content, implying that the material’s dielectric properties are very useful for electron magnetic wave absorption applications.

Hydrophobic PI/SiO2 composites with excellent dielectric property and thermal stability via simple modification

Polyimide (PI) has been extensively used in 5G microelectronics however the relatively high dielectric constant (∼3.5) and moisture adsorption have greatly limit its practical applications in high-frequency region. Here hydrophobic PI/SiO2 composite films with low dielectric constant and excellent thermal stability were synthesized by dispersing methyl modified hollow silica nanospheres (MHS) into polyamic acid solution prior to imidization treatment. Comparing with unmodified hollow silica nanospheres (HS), the MHS obtained through methyl modification can disperse uniformly in the PI matrix. Thus, the relaxation and orientation polarization of the PI chains as well as their electron migration are suppressed, resulting in a significant decrease in dielectric constant. The PI/MHS-10% film exhibits a stable low dielectric constant (1.9–2.3) in the high-frequency range (8.2 GHz–12.4 GHz), meanwhile maintains a high breakdown voltage (192 kV/mm), mechanical properties (64 MPa) and an excellent thermal stability (Td5% = 546.5 °C; Tmax = 589.0 °C). Moreover. PI/MHS demonstrates much lower linear expansion coefficient of 25.0 ppm/K that better matches the substrate. The surface contact angle of PI/MHS increases from 73° to 110° and the water absorption rate decreases from 3.1% to 1.6%, effectively avoiding the moisture adsorption. This work provides a simple method to prepare high-performance composite films for 5G practical applications.

Synthesis, physicochemical and quantum chemical studies of 7-azaindolinium-3,5-dinitrobenzoate single crystal for nonlinear optical applications

Abstract A novel hydrogen bonded single crystal of 7-azaindolinium-3,5-dinitrobenzoate (7AIDNB) has been grown, and the structure of the crystal was determined by single-crystal XRD analysis. The results show that the grown crystal belongs to a triclinic crystal system with centrosymmetric space group P-1 and the unit cell parameters: a = 6.998(9) Å, b = 8.498(12) Å, c = 13.103(17) Å, V = 710.78(17) Å3, Z = 2. The presence of expected discrete functional groups in 7AIDNB has been identified by an FT-IR spectroscopic study. The thermal stability and decomposition of the title crystal have been studied by TG-DTA analysis. The optical property of the grown crystal has been analyzed by UV-Vis-NIR spectroscopy analysis. The DFT with 6-311++G(d, p) basis set has been used to examine optimization of molecular geometry, Mulliken charge, and HOMO-LUMO. As the frequency of the grown crystal increases, the dielectric loss and dielectric constant decrease. The third-order NLO parameters of 7AIDNB have been examined by a Z-scan technique.

Studies on the Magneto-structural Properties and Initial Permittivity of Chemically Produced Nanoscale Nickel-substituted Zinc Manganese Mixed Ferrites

Objective: The objective of this work was to study in more detail the dielectric permittivity and dielectric losses at different frequencies. It is well known that adding ions increases the dielectric constant and increases the dielectric loss as well as conductivity. Furthermore, the real part of the dielectric constant decreases with increasing frequency. Dielectrics are used as a capacitor for storing energy and a transformer for insulating and cooling agents. To enhance the performance of a semiconductor device, high-permittivity dielectric materials are used. Another aim of this study was to gain a better understanding of how frequency influences the dielectric and electrical properties and what are the mathematical forms of these dependencies. With this aim, magnetic mixed metal oxide systems ZnMn1-xNixFexO4 (x=0.0, 0.25, 0.5, 0.75, and 1.0) have been synthesized in this work using wet chemical approaches. The prepared mixed-metal oxide nanomaterials have been characterized using analytical techniques, viz., XRD, FT-IR, SEM, TEM, VSM, TGA/DTA, etc. background: Spinel ferrite nanoparticles have caught the attention of researchers recently. Ferrites also feature a distinctive surface area, a porous structure, and great magnetic sensitivity. Methods: Nanoparticles of ZnMn1-xNixFexO4 (x = 0.0, 0.25, 0.5, 0.75, and 1.0) have been synthesized using the lucrative as well as eco-friendly chemical sol-gel technique. According to the Debye-Scherrer equation, the generated nanoparticles had an average crystallite size of 34 nm, and the ferrite sample showed a cubic structure. Two absorption bands at 411-455 and 595 cm-1 in FT-IR spectroscopy have evidenced the aforementioned structure to exist in the manufactured samples. The magnetic curves demonstrated that after nickel replacement, the values of coercivity and saturation magnetization altered. Between 20 Hz and 1 MHz, a dielectric behavior demonstrated conductivity and dielectric dispersion owing to interfacial polarization, as well as the interior of grain boundaries. Results: In the present case, it has been observed that the dielectric behavior decreased with increasing Ni concentration in the above-synthesized compositions. Such change may be due to the increase in resistivity of Zn-Mn ferrite with the substitution of nickel concentration and it has indicated the dielectric behavior to be directly proportional to the square root of conductivity. Conclusion: Current research has demonstrated that ferrite nanoparticles have sparked substantial interest due to their high surface-to-volume ratio, distinctive tunable capabilities, hydrophilic nature, biocompatibility, and exceptional magnetic properties. The samples' structural, microstructural, magnetic, and electrical characteristics, have also been examined.

Stress-thermal aging properties of silicone rubber used for cable accessories and electric-thermal-stress multiple fields coupling simulation

During the long-term operation of a cable, the electrical field, high temperature, and interface stress may age or deteriorate the silicon rubber (SIR) insulation of the cable accessories, affecting the combined electrical-thermal-force performance of the accessories, and easily causing discharge faults. In this work, the electrical-thermal-force properties of silicone rubber for cable accessories under thermal aging and combined force-thermal aging are studied experimentally and numerically. The changes and mechanisms of physical and chemical properties, electrical properties, thermal properties and mechanical properties of silicone rubber are tested and compared before and after aging. The changes of electric, thermal and force field of cable accessories, caused by the change of SIR material parameters under different aging time and aging form, are further simulated. The experimental results show that the crosslinking degree and molecular motion system of SIR will change with the deepening of the aging degree, which will change the electrical-thermal-force properties of the material to different degree. After aging, large agglomeration protrudes and small cavities appear in SIR section, and the damage is more serious under force-thermal aging. The relative dielectric constant first decreases and then increases with the aging time increasing. The volume resistivity, breakdown strength and flashover voltage all first increase and then decrease. The thermal conductivity first increases and then decreases with aging time increasing. In addition, with the increase of aging time, the tensile strength and elongation at break decrease gradually. Considering the change of properties after aging, the destruction of SIR material by force-thermal aging is more serious. The simulation results show that under the two aging modes, the maximum electric field strength at the stress cone root of the cable accessories first increases and then decreases with the increase of time. The electric field strength at the stress cone root of the cable accessories, caused by the force-thermal aging, changes little, maintaining about 2.2 kV/mm. The difference in temperature between the inside and the outside of the insulation layer is obvious under different aging degree, and the temperature difference shows a first decreasing and then increasing trend under both aging modes, and the maximum temperature gradient is 9.15 ℃. The interface stress at the stress cone root decreases from 0.263 to 0.230 MPa, which is about 12.5% lower. This work has guiding significance in evaluating the insulation performance and analyzing the fault of distribution cable accessories.

Electrically and magneto-dielectrically modified La3+ doped Co0.3Li0.1Ca0.5Fe2.1-xLaxO4 spinel ferrites and their potential applications

Low temperature and more efficient sol-gel auto combustion process was utilized to synthesize Co0.3Li0.1Ca0.5Fe2.1-xLaxO4 [La-CLCF] spinel ferrites (where x = 0.00, 0.01, 0.02, 0.03, 0.04, and,0.05). The La-CLCF sample's structural, optoelectrical, dielectric, and magnetic properties were examined as a result of La3+ doping. All synthesized La-CLCF samples have single-phased spinel matrix, according to X-ray diffraction (XRD) analysis. It was found that the crystallite size was 11 nm, and the bandgap energy of 3.45 eV for La3+ doping x = 0.03. The resistivity and activation energy both were increased with the substitution of La3+ in the CLCF spinel matrix, while the peak position of temperature coefficient of resistance (TCR) percentage was − 3.92%/K at 372 K for sample x = 0.03. The alternating current conductivity improves with frequency, whereas the dielectric constant and tangent loss decrease as frequency increases. Further, the saturation magnetization and the microwave operating frequency for all the samples were reduced with the doping of La3+. The minimum coercivity was 242 Oe at x = 0.03. Our study suggested that the Co0.3Li0.1Ca0.5Fe2.07La0.03O4 sample is tested as an active material for potential use in high-frequency applications, electromagnetic wave absorbing material, and evaluating the sensitivity of infrared (IR) detectors used in night vision bolometers.